Abstract:

A pulse power source which can perform high repetition of pulse signals by
enhancing the throughput of a pulse source is provided. The pulse power
source includes: a charger; an initial-stage capacitor section which is
provided with a capacitor charged by the charger; and a magnetic pulse
compression circuit which performs magnetic pulse compression of a pulse
current generated by discharging a charge from the capacitor at the
initial-stage capacitor section and, thereafter, outputs the pulse
current. An exposure device which includes the pulse power source is also
provided. The pulse power source includes, between the initial-stage
capacitor section and the magnetic pulse compression circuit, a
transistor which controls timing of discharging a charge from the
initial-stage capacitor section, an inductor which constitutes a
resonance circuit together with the capacitor at the initial stage
capacitor section, and a diode which rectifies the pulse current. The
pulse power source further includes a means for preventing the generation
of an electric current in the reverse direction in the pulse current.

Claims:

1. A high repetition pulse power source comprising:a charger;an
initial-stage capacitor section having a capacitor which is charged by
the charger; anda magnetic pulse compression circuit for compressing and
outputting a pulse current generated by discharging a charge of the
capacitor, whereinthe high repetition pulse power source includes,
between the initial-stage capacitor section and the magnetic pulse
compression circuit, a semiconductor switch for controlling timing at
which the charge of the capacitor of the initial-stage capacitor section
is discharged, a saturable reactor or a saturable inductor which is
provided between the initial-stage capacitor section and the magnetic
pulse compression circuit, and incorporates an inductor which constitutes
a resonance circuit together with the capacitor of the initial-stage
capacitor section therein, and a diode for preventing a reverse current;
andthe high repetition pulse power source further includes, for
preventing the generation of a transitional current which flows in the
backward direction in a pulse current, a coil formed of secondary winding
wound around a core around which first winding which constitutes the
inductor is wound, and a reset current generating circuit for supplying a
predetermined current which magnetizes the core in the forward direction
to the coil.

2. (canceled)

3. A high repetition pulse power source according to claim 1, wherein an
electrostatic capacitance of the initial-stage capacitor section is
approximately ten times or more larger than an electrostatic capacitance
of capacitors provided in the magnetic pulse compression circuit.

4. A high repetition pulse power source according to claim 1, wherein
capacitors are provided in the magnetic pulse compression circuit in a
plurality of stages, and electrostatic capacitances of the capacitors are
sequentially increased in order from the capacitor on an input side to
the capacitor on an output side.

5. An exposure device including the high repetition pulse power source
described in claim 1.

6. An exposure device according to claim 5, wherein the exposure device
comprises:a light source which radiates light for exposure with the
supply of an electric current outputted from the high repetition pulse
power source;a light quantity measuring means which measures a quantity
of light radiated from the light source; andan adjusting means which
adjusts the number of times of light emission of the light source based
on a result of measurement obtained by the light quantity measuring
means.

7. An exposure device according to claim 6, wherein the capacitor in the
initial-stage capacitor section is charged during a period where the
exposure by the light source is stopped.

8. An exposure device according to claim 5, wherein an exposure quantity
is controlled corresponding to the number of pulses outputted from the
high repetition pulse power source.

Description:

BACKGROUND OF THE INVENTION

[0001]The present invention relates to a high repetition pulse power
source and an exposure device with the high repetition pulse power
source.

[0002]Recently, a technique which is referred to as a pulse power
technique has been attracting attentions. In this pulse power technique,
a charge stored in a charge storing means such as a capacitor is
outputted instantaneously thus generating large electric power. By using
such a technique as a drive device of a semiconductor-lithography excimer
laser, a large quantity of current of high voltage is generated, quality
of water is improved by applying large electric power instantaneously,
micro holes are formed in a cell membrane, or plasma is generated for
etching a semiconductor or for forming a film.

[0003]In such a pulse power technique, a pulse power source is used for
generating large electric power instantaneously. The pulse power source
includes an initial-stage capacitor for storing a charge, a magnetic
pulse compression circuit which compresses a pulse current which is
generated by discharging the charge from the initial-stage capacitor, and
a charger which charges the initial-stage capacitor with a charge. The
pulse power source can input a pulse current whose pulse width is
compressed to a predetermined load (see patent document 1, for example).

[0004]As one of semiconductor-element manufacturing devices which use such
a pulse power source, an exposure device used in a lithography step is
known. Particularly, with respect to the exposure device, along with the
refinement of manufacture process rules of semiconductor elements formed
on a semiconductor substrate, the further shortening of a wavelength of
radiation light is requested so that ultraviolet rays are often used
currently.

[0005]Further, to radiate extreme ultraviolet rays having a shorter
optical wavelength, it is necessary to use a special light source such as
an EUV (Extreme Ultra-Violet) lamp. Further, a light source is requested
to possess a large quantity of light as much as possible. Accordingly, a
high repetition pulse compression power source is used as a means for
supplying a large pulse current for allowing the EUV lamp to emit light.

[0006]Further, in the exposure device, for enhancing the manufacturing
efficiency, there has been a demand for the high repetition performance
which can increase the number of times of radiation per unit time as much
as possible by increasing a throughput.

[0007]In view of the above, inventors of the present invention have
proposed, as a pulse power source which satisfies such demands, a pulse
power source shown in a circuit diagram of FIG. 4.

[0008]The pulse power source includes an initial-stage capacitor 120 which
has one end thereof connected to a charger 110 and the other end thereof
connected to a ground, and first to fourth capacitors 131 to 134 for
compression which are sequentially charged by resonance charging along
with discharging of a charge stored in the initial-stage capacitor and
compress electric energy by gradually shortening a pulse width of a pulse
current generated along with each discharge. A pulse current which is
generated along with discharging of a charge from the fourth capacitor
134 is inputted to the EUV lamp 141 which constitutes a load so as to
allow the EUV lamp 141 to emit an EUV light.

[0009]A booster pulse transformer 135 is provided arranged between the
first capacitor 131 and the second capacitor 132, and a voltage is
amplified by the booster pulse transformer 135.

[0010]The initial-stage capacitor 120 and the first to fourth capacitors
131 to 134 have one end thereof connected to a ground respectively, while
at the other end of each component not connected to the ground, the
initial-stage capacitor 120 and the first capacitor 131 are connected
with each other via an inductor 121, a diode 122 and a semiconductor 123,
and the first capacitor 131 is charged by resonance charging using an
oscillation circuit constituted of the initial-stage capacitor 120 and
the inductor 121. In FIG. 4, numeral 124 indicates a protective diode of
a semiconductor switch 123. The control-use semiconductor switch 123 is
constituted of an insulation gate bipolar transistor.

[0011]A booster pulse transformer 135 is provided between the first
capacitor 131 and the second capacitor 132, and a first saturable
inductor 136 is provided between the first capacitor 131 and the booster
pulse transformer 135 and on an end portion side where the first
capacitor 131 is not connected to the ground. The second capacitor 132 is
charged by resonance charging using an LC resonance circuit which is
constituted of the first saturable inductor 136 and the first capacitor
131.

[0012]The second capacitor 132 and the third capacitor 133 are connected
with each other via a second saturable inductor 137 on an end portion
side where the second capacitor 132 and the third capacitor 133 are not
connected to the ground, the third capacitor 133 is charged by resonance
charging using an LC resonance circuit which is constituted of the second
saturable inductor 137 and the second capacitor 132.

[0013]The third capacitor 133 and the fourth capacitor 134 are connected
with each other via a third saturable inductor 138 on an end portion side
where the third capacitor 133 and the fourth capacitor 134 are not
connected to the ground, and the fourth capacitor 134 is charged by
resonance charging using an LC resonance circuit which is constituted of
the third saturable inductor 138 and the third capacitor 133.

[0014]The fourth capacitor 134 is connected with a load 140 via a fourth
saturable inductor 139, and discharges a charge to a load 140 by an LC
resonance circuit which is constituted of the fourth saturable inductor
139 and the fourth capacitor 134. Here, a magnetic pulse compression
circuit is constituted of four capacitors for compression consisting of
first to fourth capacitors 131 to 134 and the first to fourth saturable
inductors 136 to 139. However, the number of the magnetic pulse
compression stages of C-L-C may be one or greater.

Patent document 1: JP-A-11-145794

SUMMARY OF THE INVENTION

[0015]However, in the pulse power source shown in the circuit diagram of
FIG. 4, in generating a high-frequency pulse current by performing an
ON/OFF control of the control-use semiconductor switch 123 at a high
speed, a reverse current is transitionally generated in the pulse current
as shown in FIG. 5 due to the characteristic of the diode 122.

[0016]Accordingly, in using the pulse power source, the pulse power source
can be used only under a limited frequency condition during a reverse
recovering time of the diode and hence, there exists a drawback that the
throughput of the high repetition pulse power source cannot be enhanced.

[0017]Further, in an exposure device which uses such a pulse power source,
it is impossible to further shorten a time necessary for exposure for one
time and hence, it is difficult to shorten a time necessary for exposure
processing thus giving rise to a drawback that the enhancement of
operational efficiency is difficult.

[0018]The present invention is directed to a high repetition pulse power
source which includes: a charger; an initial-stage capacitor section
having a capacitor which is charged by the charger; and a magnetic pulse
compression circuit for compressing and outputting a pulse current
generated by discharging a charge of the capacitor, wherein the high
repetition pulse power source includes, between the initial-stage
capacitor section and the magnetic pulse compression circuit, a
semiconductor switch for controlling timing at which the charge of the
capacitor of the initial-stage capacitor section is discharged, a
saturable reactor or a saturable inductor which is provided between the
initial-stage capacitor section and the magnetic pulse compression
circuit, and incorporates an inductor which constitutes a resonance
circuit together with the capacitor of the initial-stage capacitor
section therein, and a diode for preventing a reverse current, and the
high repetition pulse power source further includes, for preventing the
generation of a transitional current which flows in the backward
direction in a pulse current, a coil formed of secondary winding wound
around a core around which first winding which constitutes the inductor
is wound, and a reset current generating circuit for supplying a
predetermined current which magnetizes the core in the forward direction
to the coil. Due to such a constitution, it is possible to prevent the
generation of the reverse current in the pulse current by the reverse
current prevention means so that the throughput of the high repetition
pulse power source can be enhanced thus enabling the higher repetition
performance. Further, the resonance circuit for discharging a charge of
the initial-stage capacitor section can be made compact.

[0019]Further, the pulse power source according to the present invention
possesses the following technical features.

[0020](1) The reverse current prevention means is a saturable reactor or a
saturable inductor which incorporates the inductor therein and is
provided between the initial-stage capacitor section and the magnetic
pulse compression circuit, and a reset current generating circuit which
resets the saturable reactor or the saturable inductor is provided in the
forward direction.

[0021](2) An electrostatic capacitance of the initial-stage capacitor
section is approximately ten times or more larger than an electrostatic
capacitance of capacitors provided in the magnetic pulse compression
circuit.

[0022](3) Capacitors are provided in the magnetic pulse compression
circuit in a plurality of stages, and electrostatic capacitances of the
capacitors are sequentially increased in order from the capacitor on an
input side to the capacitor on an output side.

[0023]The present invention is also directed to an exposure device which
includes the high repetition pulse power source, the exposure device
including: a light source which radiates light for exposure with the
supply of an electric current outputted from the high repetition pulse
power source; a light quantity measuring means which measures a quantity
of light radiated from the light source; and an adjusting means which
adjusts the number of times of light emission of the light source based
on a result of measurement obtained by the light quantity measuring
means. The exposure device of the present invention is also characterized
in that the capacitor in the initial-stage capacitor section is charged
during a period where the exposure by the light source is stopped.

[0024]The exposure device of the present invention is further
characterized in that an exposure quantity is controlled corresponding to
the number of pulses outputted from the high repetition pulse power
source. Due to such a constitution, the number of times of radiation per
unit time can be increased and hence, a radiation quantity of light per
unit time can be increased whereby a time necessary for exposure
processing can be shortened thus enhancing operation efficiency.

[0025]According to the present invention, by providing, between the
initial-stage capacitor section and the magnetic pulse compression
circuit, not only the diode but also the coil formed of the secondary
winding wound around the core around which the first winding which
constitutes the inductor is wound, and the reset current generating
circuit for supplying the predetermined current which magnetizes the core
in the forward direction to the coil for preventing the generation of an
electric current which flows in the backward direction in a pulse
current, it is possible to prevent the generation of the reverse current
in the pulse current by the reverse current prevention means and hence,
the throughput of the high repetition pulse power source can be enhanced
thus further enhancing the high repetition performance of pulse signals.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is an explanatory view of an exposure device according to an
embodiment of the present invention;

[0027]FIG. 2 is a waveform diagram showing a waveform of a pulse current
which flows in a diode portion of the pulse power source according to the
embodiment of the present invention;

[0028]FIG. 3 is a timing chart showing driving timing of a semiconductor
switch;

[0029]FIG. 4 is an explanatory view of a conventional pulse power source;
and

[0030]FIG. 5 is a waveform diagram showing a reverse current portion
appearing in a pulse current which flows in a diode portion of the
conventional pulse power source.

DETAILED DESCRIPTION OF THE INVENTION

[0031]The present invention is directed to a high repetition pulse power
source and an exposure device which includes the high repetition pulse
power source. In such a high repetition pulse power source which includes
a charger, an initial-stage capacitor section which includes a capacitor
charged by the charger, and a magnetic pulse compression circuit which
performs magnetic pulse compression of a pulse current generated by
discharging a charge from the capacitor of the initial-stage capacitor
section and outputs a compressed pulse current, the high repetition pulse
power source includes a reverse-current preventing means which prevents
the generation of an electric current which flows in the reverse
direction in the pulse current between the initial-stage capacitor
section and the magnetic pulse compression circuit.

[0032]That is, a diode is provided between the initial-stage capacitor
section and the magnetic pulse compression circuit for preventing a
reverse current flow. However, there exists a possibility that an
electric current which flows in the reverse-current direction is
generated in the pulse current attributed to lowering of a rectifying
characteristic of the diode with respect to high frequency. By
interrupting the electric current which flows in the reverse direction
which cannot be interrupted by the diode using the reverse-current
preventing means, frequency of pulse current is increased thus enhancing
throughput of the pulse power source.

[0033]An embodiment of the present invention is explained in detail
hereinafter. In this embodiment, the high repetition pulse power source
incorporated into the exposure device is explained. However, the present
invention is not limited to a case where the high repetition pulse power
source is used as a part of the exposure device but can be also used in
the same manner as a conventionally-used pulse power source incorporated
in a plasma generating device or an ozone generating device, for example.

[0034]As shown in FIG. 1, the exposure device A includes the high
repetition pulse power source 10, an EUV lamp 41 which is connected to
the high repetition pulse power source 10, a photo sensor 51 which
constitutes a light quantity measuring means for detecting a quantity of
light radiated from the EUV lamp 41, and a control part 52 which detects
an output signal which is a measurement result outputted from the photo
sensor 51 and calculates the quantity of light by analyzing the output
signal.

[0035]The high repetition pulse power source 10 includes an initial-stage
capacitor section 20 constituted of a plurality of capacitors 21 each of
which has one end thereof connected to a charger 11 and the other end
thereof connected to a ground, and first to fourth capacitors 31 to 34
for compression which compress electric energy by sequentially performing
resonance charging along with discharging of a charge stored in the
initial-stage capacitor section 20 and by gradually decreasing a cycle of
a pulse current generated along with discharging by each capacitor,
wherein energy outputted from the fourth capacitor 34 is inputted to the
EUV lamp 41 which constitutes a load so that EUV light is radiated from
the EUV lamp 41.

[0036]A boosting pulse transformer 35 is provided between the first
capacitor 31 and the second capacitor 32, and a voltage is amplified by
this boosting pulse transformer 35.

[0037]The respective capacitors 21 of the initial-stage capacitor section
20 and the first to fourth capacitors 31 to 34 have one end thereof
connected to a ground respectively.

[0038]The initial-stage capacitor section 20 and the first capacitor 31
are connected to each other via a semiconductor switch 12 formed of a
transistor, a diode 13 and an inductor 14a on an end portion side where
the initial-stage capacitor section 20 and the first capacitor 31 are not
connected to a ground. The first capacitor 31 is charged by resonance
charging using an LC resonance circuit which is constituted of the
initial-stage capacitor section 20 and the inductor 14a. In FIG. 1,
numeral 15 indicates a protective diode for the semiconductor switch 12.
The semiconductor switch 12 is formed of an insulation gate bipolar
transistor in this embodiment.

[0039]The boosting pulse transformer 35 is provided between the first
capacitor 31 and the second capacitor 32 and, at the same time, a first
saturable inductor 36 is provided between the first capacitor 31 and the
boosting pulse transformer 35 on an end portion side of the first
capacitor 31 which is not connected to a ground. The second capacitor 32
is charged by resonance charging using the LC resonance circuit
constituted of the first saturable inductor 36 and the first capacitor
31.

[0040]The second capacitor 32 and the third capacitor 33 are connected to
each other via a second saturable inductor 37 on an end portion side
where the second capacitor 32 and the third capacitor 33 are not
connected to a ground, and the third capacitor 33 is charged by resonance
charging using the LC resonance circuit constituted of the second
saturable inductor 37 and the second capacitor 32.

[0041]The third capacitor 33 and the fourth capacitor 34 are connected to
each other via a third saturable inductor 38 on an end portion side where
the third capacitor 33 and the fourth capacitor 34 are not connected to a
ground, and the fourth capacitor 34 is charged by resonance charging
using an LC resonance circuit constituted of the third saturable inductor
38 and the third capacitor 33.

[0042]The fourth capacitor 34 is connected to the EUV lamp 41 via a fourth
saturable inductor 39, and discharging of a charge to the EUV lamp 41 is
performed by an LC resonance circuit constituted of the fourth saturable
inductor 39 and the fourth capacitor 34. In this embodiment, a magnetic
pulse compression circuit is constituted of four capacitors for
compression consisting of the first to the fourth capacitors 31 to 34 and
the first to the fourth saturable inductors 36 to 39. However, the number
of C-L-C compression stages may be 1 or greater.

[0043]In the high repetition pulse power source 10 having such a
constitution, the gist of the present invention lies in that a
reverse-current preventing means which prevents a reverse current of a
pulse current generated by resonance attributed to the capacitor 21 of
the initial-stage capacitor section 20 and the inductor 14a is provided
between the initial-stage capacitor section 20 and the first capacitor 31
of the magnetic pulse compression circuit.

[0044]By preventing the reverse current generated in the pulse current
using the reverse-current preventing means, even when frequency of the
pulse current is set to frequency higher than an upper limit of frequency
restricted based on a characteristic of the diode 13, a reverse current
is prevented by the reverse-current preventing means and hence, frequency
of the pulse current can be increased.

[0045]Accordingly, throughput of the high repetition pulse power source 10
can be enhanced thus further enhancing the high repetition performance of
pulse signals.

[0046]Here, the reverse-current preventing means is constituted of a
saturable reactor 14 or a saturable inductor incorporating the inductor
14a therein which is provided between the initial-stage capacitor section
20 and the first capacitor 31 of the magnetic pulse compression circuit.

[0047]Particularly, the saturable reactor 14 or the saturable inductor is
provided between the initial-stage capacitor section 20 and the first
capacitor 31 of the magnetic pulse compression circuit and, at the same
time, a reset current generating circuit 16 which resets the saturable
reactor 14 or the saturable inductor is provided in the forward
direction.

[0048]That is, the reset current generating circuit 16 is configured such
that a resetting coil 14b is formed of secondary winding wound around a
core around which first winding which constitutes the inductor 14a of the
saturable reactor 14 or the saturable inductor is wound, and a
predetermined electric current which magnetizes the core in the forward
direction is supplied to the resetting coil 14b.

[0049]Accordingly, when a reverse current is generated in a pulse current
by increasing frequency of the pulse current, by magnetizing the core in
the forward direction by supplying a predetermined current to the
resetting coil 14b from the reset current generating circuit 16, a
reverse current can be surely interrupted as shown in FIG. 2.

[0050]Here, the inductor 14a incorporated in the saturable reactor 14 or
the saturable inductor constitutes the reverse current preventing means
and, at the same time, constitutes a resonance circuit together with the
capacitor 21 of the initial-stage capacitor section 20. By charging the
first capacitor 31 by resonance charging using such a resonance circuit,
the high repetition pulse power source 10 can be formed in a compact
shape.

[0051]Further, by constituting the initial-stage capacitor section 20
using a plurality of capacitors 21 which are connected to each other in
parallel such that the initial-stage capacitor section 20 possesses
sufficiently large capacitance compared to the first capacitor 31, a
voltage charged to the initial-stage capacitor section 20 can be lowered
and hence, the charger 11 can be miniaturized. The high repetition pulse
power source 10 can be miniaturized along with this miniaturization of
the charger 11. Particularly, it is desirable that the electrostatic
capacitance of the initial-stage capacitor section 20 is approximately
ten times or more larger than the electrostatic capacitance of the first
to fourth capacitors 31 to 34 provided in the magnetic pulse compression
circuit.

[0052]Here, the electrostatic capacitance of the second to fourth
capacitors 32 to 34 are set, for effectively performing the pulse
compression, in order of C32≦C33≦C4, wherein
the capacitance of the second capacitor 32 is expressed by C32, the
third capacitor 33 is expressed by C33, and the fourth capacitor 34
is expressed by C34. That is, the electrostatic capacitances of the
capacitors are sequentially increased in order from the capacitor on an
input side to the capacitor on an output side.

[0053]In the exposure device A having the high repetition pulse power
source 10 which has the above-mentioned constitution, due to the
enhancement of the high repetition of pulse signals generated by the high
repetition pulse power source 10, light emission intervals for allowing
the EUV lamp 41 to emit light can be shortened so that a time necessary
for exposure processing can be shortened thus enhancing an operation
efficiency.

[0054]Particularly, in the exposure device A, usually, a curing reaction
of a resist is generated by radiating a predetermined quantity of light
to a semiconductor substrate coated with the resist. In this case,
instead of the performing the exposure processing by radiating the
predetermined quantity of light by performing the continuous emission of
light one time from the ECU lamp 41, the exposure processing can be
performed by allowing the EUV lamp 41 to intermittently emit light by
controlling the number of pulses by the high repetition pulse power
source 10 until the cumulative light quantity reaches the predetermined
light quantity.

[0055]By performing exposure processing by allowing the EUV lamp 41 to
intermittently emit light, it is possible to alleviate design conditions
of electric characteristics such as a withstand voltage of the high
repetition pulse power source 10 and hence, the high repetition pulse
power source 10 can be made further compact. Further, the deterioration
of the EUV lamp 41 which takes place along with heating of the EUV lamp
41 can be suppressed thus realizing the extension of lifetime of the EUV
lamp 41.

[0056]Here, in the exposure device A, a quantity of light radiated from
the EUV lamp 41 is detected by a photo sensor 51, a result of the
detection is inputted to the control part 52 as an output signal, and the
control part 52 calculates a quantity of light for each radiation and
calculates a cumulative quantity of light based on calculated quantities
of respective radiated lights, and exposure processing is finished at a
point of time that the cumulative quantity of light reaches a
predetermined quantity of light.

[0057]Particularly, until the cumulative quantity of light reaches the
predetermined quantity of light, the control part 52 inputs a drive
signal which brings the semiconductor switch 12 of the high repetition
pulse power source 10 into an ON state at predetermined timing shown in
FIG. 3 to the semiconductor switch 12 thus charging the first capacitor
31 by resonance charging and outputting a pulse current.

[0058]That is, the control part 52 functions as an adjustment means which
adjusts the number of light emission times of the EUV lamp 41 by
performing the drive control of the semiconductor switch 12 and hence,
the control part 52 can extremely easily perform the light emission
control of the EUV lamp 41.

[0059]In this manner, by calculating the cumulative quantity of light by
the control part 52, even when the EUV lamp 41 is deteriorated with time
so that a quantity of light which is radiated by emission of light per
one time is lowered, the quantity of light in total can be set to the
predetermined quantity of light or more so that the irregularities in
manufacture can be suppressed.

[0060]According to this embodiment, the control part 52 performs not only
the drive control of the semiconductor switch 12 but also a drive control
of the reset current generation circuit 16. A core of the saturable
reactor 14 or the saturable inductor may be magnetized in the forward
direction at predetermined timing by driving the reset current generation
circuit 16 based on a control signal from the control part 52.

[0061]Further, the control part 52 also performs a drive control of the
charger 11. That is, the control part 52 operates the charger 11 so as to
charge the initial-stage capacitor section 20 when the exposure by the
EUV lamp 41 which constitutes a light source is stopped thus efficiently
charging the initial-stage capacitor section 20 and hence, it is possible
to allow the high repetition pulse power source 10 to readily start the
predetermined outputting whereby operational efficiency can be enhanced.